Phase relationship of complex multi-component system in chromate cleaner production

Abstract

The relationships of the complex multi-component systems in the liquid-phase oxidization and separation process related with the chromate cleaner production are investigated theoretically and experimentally. The phase diagram of main system Fe-Cr₂O₂O₄-KOH-O₂ of oxidization process and the relationship of its standard Gibbs free energy change with temperature are calculated. A series of phase diagrams of the separation process at different temperatures, such as K(Na)OH-K(Na)₂CrO₄-H₂O, KOH-KAIO₂-H₂O, K(Na)OH-K(Na)₂CO₃-H₂O, K(Na)OH-K(Na)HCO₃-H₂O and K(Na)HCO₃-K(Na)₂CrO₄-H₂O have also been calculated. Some experiments are carried out to verify the calculated results. Our results showed that the sub-molten salt media are suitable for the oxidization and separation processes; FeCr₂O₄ can be Oxidized across a wide range of temperature; K(Na)₂CrO₄ can be separated from K(Na)AlO₂ system at appropriate temperature and proper concentration; the crystallization of carbonate is easier than that of K(Na)₂CrO₄.

^*Supported by National Natural Science Foundation of China (Grant No. 50234040) and National Science Fund for Distinguished Young Scholars of China (Grant No. 50425415)

Keywords:

• chromite
• chromate system
• thermodynamics calculation
• phase diagram

Notes

^*Supported by National Natural Science Foundation of China (Grant No. 50234040) and National Science Fund for Distinguished Young Scholars of China (Grant No. 50425415)